Apparatus for extruding tubular members from solid billets



Nov. 4, 1969 A. M. MURPHY ETAL APPARATUS FOR EXTRUDING TUBULAR MEMBERS FROM SOLID BILLETS Filed Nov. 5, 1966 4 Sheets-Sheet 1 INVENTORS ALFRED M.MURPHY CARL M. FILAK THOMAS E LONG JOHN A. BROWN,JR. BY flu w THEIR ATTOR NEYS Nov. 4, 1969 A. M. MURPHY ETAL 3,475,942

APPARATUS FOR EXTRUDING TUBULAR MEMBERS FROM SOLID BILLETS Filed Nov. 5, 1966 4 Sheets-Sheet 2 IN TOR A E .MUR C M. FIL

THEIR ATTORNEYS OMAS P. 0 JOHN A. BROWN,JR.

Nov. 4, 1969 A. M. MURPHY ETAL 3,475,942

APPARATUS FOR EXTRUDING TUBULAR MEMBERS FROM SOLID BILLETS Filed Nov. 5, 1966 4 Sheets-Sheet 5 FIG.8

INVENTORS ALFRED M. MURPHY CARL M. FILAK THOMAS E LONG JOHN A. ROWN, JR. BY m w )iowafl r rm THEIR ATTORNEYS 7 Nov. 4. 1969 APPARATUS FOR EXTRUDING TUBULAR MEMBERS Filed NOV. 5, 1966 A. M. MURPHY E FIG.9

FROM SOLID BILLETS 4 Sheets-Sheet 4 INVENTORS ALFRED M. MULRPHY THOMAS E LONG JOHN A. BROWN,JR. BY 41m kw K THEIR ATTOR United States Patent U.S. Cl. 72-265 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to an apparatus for piercing and extruding a solid metallic billet through a female die to form an extruded tubular length with a mandrel that pierces into the solid billet until a tip of the mandrel is telescoped into the female die to a predetermined position relative thereto to define an annular cavity between an extruding surface of the mandrel tip and the female die whereby the billet can be extruded through the annular cavity to form the extruded tubular length, the mandrel having an exchangeable collar defining the extruding surface thereof with the collar having a first substantially cylindrical part and a second substantially cylindrical part spaced from the first part by an inwardly directed stepped part of the collar.

This invention relates to an improved apparatus for extruding a hollow tubular length from a solid metallic billet or the like, as well as to improved parts for such an apparatus or the like.

It is well known that it is relatively difficult to extrude a hollow tubular member from a solid aluminum-containing metallic billet because of the inherent characteristics of the aluminum-containing metallic material. For example, the softer aluminum alloys tend to stick to the piercing part of the mandrel means and build up layers thereon which adversely affect the internal dimensions and surfaces of the resulting tubular members, such gumminess of the built-up layers requiring time-consuming and expensive removal operations such as by physically filing the layers off the extruding surface means or chemically removing the same.

Further, the radial pressures imposed on such billet piercing and extruding mandrel means during the piercing of such solid metallic billets tend to weaken and damage the various joints of the mandrel means.

Therefore, in the past, hollow tubular members were extruded from aluminum-containing metallic material by first forming a solid cylindrical billet of the aluminumcontaining metallic material and, thereafter, drilling a hole longitudinally through the center of the billet or by casting such a hollow billet so that a mandrel could be inserted therein and cooperate with an outer die means to extrude the hollow billet into a tubular member.

However, according to the teachings of the copending patent application, Ser. No. 317,463, filed Oct. 23, 1963, and now Patent No. 3,296,848 and assigned to the same assignee to whom this application is assigned an improved apparatus and method are provided wherein the tubular member can be extruded from a solid metallic billet or the like, regardless of whether the billet is formed from soft alloys or not, without requiring a hollowing of the solid billet before the same is placed in the extruding apparatus of this invention or the casting of a hollow billet, because the piercing and extruding mandrel means is provided with a readily exchangeable and uniquely shaped extruding surface means that substantially eliminates the aforementioned problems whereby a more ecoice nomical and accurate extruding method and apparatus are provided.

Therefore, this invention provides improvements in the apparatus disclosed and claimed in the aforementioned copending patent application in regard to the piercing and extruding mandrel means thereof, as well as in regard to the exchangeable extruding surface means thereof.

Accordingly, it is an object of this invention to provide an improved apparatus for extruding a hollow tubular member or the like from a solid metallic billet or the like, the apparatus of this invention having one or more of the novel features as set forth above or hereinafter shown or described.

Another object of this invention is to provide improved parts for such an apparatus or the like.

Other objects, uses and advantages of this invention are apparent from a reading of this description, which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIGURE 1 is a cross-sectional, fragmentary view illustrating the apparatus of this invention.

FIGURE 2 is a fragmentary view similar to FIGURE 1 and illustrates the apparatus in another operating position thereof.

FIGURE 3 is an enlarged, fragmentary, cross-sectional view illustrating the cooperation between the mandrel means of this invention and the hollow stem of the apparatus of FIGURE 1.

FIGURE 4 is a view similar to FIGURE 3 and illustrates the operation of the dummy block of the apparatus of FIGURE 1.

FIGURE 5 is a view similar to FIGURE 2 and illustrates the apparatus of this invention in another operating position thereof.

FIGURE 6 is an enlarged, fragmentary, cross-sectional view illustrating the cooperation between the exchangeable extruding surface means of the mandrel means and the outer extruding female die means of the apparatus of this invention.

FIGURE 7 is an enlarged, cross-sectional view taken on line 77 of FIGURE 5 with background structure removed.

FIGURE 8 is an exploded perspective of the various parts of the mandrel means of this invention.

FIGURE 9 is an enlarged view similar to FIGURE 6 and illustrates another embodiment of this invention.

FIGURE 10 is a reduced perspective view of the extruding surface means of the mandrel means of FIG- URE 9.

While the various features of this invention are hereinafter described and illustrated as being particularly adaptable for extruding a hollow tubular member from an aluminum-containing metallic billet or the like, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to extrude other structures from other types of metallic material or the like.

Therefore, this invention is not to be limited to only the embodiment illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIGURE 1, the improved apparatus of this invention is generally indicated by the reference numeral 10 and comprises means for extruding a hollow tubular member 11, FIGURES 5, from a substantially solid and cylindrical metallic billet 12, FIGURE 1, in a manner hereinafter described.

As illustrated in FIGURE 1, the apparatus 10 comprises a hollow stationary housing 13 carrying a sleeve 14 which defines a cylindrical cavity 15 therein for receiving the heated billet 12. t

A plurality of collar means 16, 17, 18, 19, 20 and 2 are respectively carried by stationary frame structures 22 and 23 in such a manner that the collars 16-21 define a passage means 24 leading to the left-hand end of the cavity of the sleeve 14.

The collar 21 cooperates with a die retaining member 25 to hold an annular die member 26 adjacent the lefthand end of the cavity 15 in a manner illustrated in FIG- URE 1, the extruding die member 26 having a die insert 27 to form the outer extruding die means of the apparatus 1 in a manner hereinafter described.

As illustrated in FIGURE 1, the die means 27 is adapted to be disposed against the left-hand end 28 of the solid billet 12 for a purpose hereinafter described.

A piercing and extruding mandrel means 29 is carried by the apparatus 10 and is adapted to be moved relative to the housing 13 in a manner hereinafter described, the piercing and extruding mandrel means 29 including a collar means 30 and a plurality of adapters 31, 32, 33, 34 and 35 secured together in aligned relation by threaded connections therebetween.

The adapter 35 of the piercing and extruding mandrel means 29 is carried by a retaining means 36 which is adapted to be moved to the left or to the right by suitable ram means for a purpose hereinafter described, the ram means being pneumatically, hydraulically or mechanically operated, as desired.

A hollow stem 37 surrounds the forward portion of the mandrel means 29 and is adapted to have the end 38 thereof telescopically received in the cavity 15 of the housing 13 for a purpose hereinafter described. The other end 39 of the hollow stem 37 is secured to a movable housing structure 40 in any suitable manner, such as by a retaining collar 41 and a wedge member 42 cooperating with a tapering surface 43 of the stem 37 to wedge the end 39 against a retainer 44 carried by the housing 40.

Suitable ram means are operatively interconnected to the housing 40 to cause the same to move to the right or the left in FIGURE 1 for a purpose hereinafter described, the ram means being hydraulically, pneumatically or mechanically operated as desired.

As illustrated in FIGURES 1 and 3, the adapter 31 and collar means 30 of the piercing and extruding mandrel means 29 have outside diameters thereof substantially smaller than the inside diameter of the stem 37 to facilitate relative movement therebetween.

However, the adapter 31 of the piercing and extruding mandrel means 29 has a plurality of circumferential lands 45, FIGURES 1 and 3, adapted to slidingly engage the internal peripheral surface 46 of the stem 37 to maintain die means 27 for a purpose hereinafter described. alignment of the collar means 30 relative to the outer As illustrated in FIGURES 1 and 4, an annular dummy block 47 is disposed in the cavity 15 of the housing 13 between the end 48 of the billet 12 and the end 38 of the stem 37, the dummy block 47 having a plurality of outer circumferential lands 49 adapted to slidingly and sealingly engage the internal peripheral surface 50 of the sleeve member 14 of the housing 13 in the manner illustrated in FIGURE 4 to prevent the billet 12 from extruding to the right in FIGURE 1 during the extruding operation on the billet 12 in the manner hereinafter described. Similarly, the dummy block 47 has a plurality of inwardly directed annular lands 51 adapted to sealingly and slidingly engage the external peripheral surface 52 of the adapter 31 of of the piercing and extruding mandrel means 29 in the manner illustrated in FIGURE 4 to prevent rightward extrusion of the billet 12 during the extruding operation hereinafter described.

As illustrated in FIGURES 6 and 8, the adapter 31 has a substantially cylindrical part 53 extending from the previously described left-hand land 45 thereof and interconnecting with the larger end 54 of a substantially frusto-conical part 55 having its smaller end 56 interconnected to a substantially cylindrical part 57 having a diameter smaller than the diameter of the cylindrical part 53 of the adapter 31. A reduced portion or free end 58 of the piercing and extruding mandrel means 29 extends concentrically and integrally from the foreword flat end surface 59 of the previously described cylindrical part 57 to carry the exchangeable collar means 30 previously described, the flat end surface 59 of the adapter 31 defining a locating shoulder means in a manner hereinafter described.

The extending free end means 58 of the piercing and extruding mandrel means 29 includes a substantially cylindrical portion 60 and another substantially cylindrical portion 61 spaced therefrom with the cylindrical portion 61 being externally threaded for a purpose hereinafter described, the cylindrical portion 60 being respectively separated from the shoulder means 59 of the adapter 31 and the threaded portion 61 thereof by annular stress relieving grooves or recesses 62 and 63 for a purpose hereinafter described. The groove 62 being so formed that the same also interrupts the flat end surface or shoulder means 59 of the adapter 31 as illustrated in FIGURE 8.

The extreme left-hand end of the free end 58 of the piercing and extruding mandrel means 29 is substantially bullet shaped or conical in the manner illustrated by the referenced numeral 64 in FIGURES 6 and 8 to enhance the piercing operation of the mandrel means 29 and permit the same to pierce and extrude solid billets of soft aluminum alloys as will be apparent hereinafter.

The exchangeable coller means 30 of this invention can be formed of tungsten carbide or other hard metallic material as well as from ceramic or other types of hard material such as hardened or tool steel, as desired. In any event, the collar means 30 is formed with opposed fiat parallel end surfaces 65 and 66 respectively interrupted by a substantially cylindrical bore 67 passing longitudinally therethrough and being of a size to permit the collar means 30 to be telescopically disposed on the cylindrical part 60 of the free end 58 of the mandrel means 29, with the cylindrical part 60 properly positioning the collar means 30 relative to the longitudinal axis of the piercing and extruding mandrel means 29. The opposed end surfaces 65 and 66 of the collar means 30 are respectively provided with beveled surfaces 68 and 69 adjacent the cylindrical bore 67 thereof for stress relief purposes, the leading or forward end surface 65 of the collar means 30 also having its outer edge formed with a bevel 70 as illustrated to facilitate the billet piercing operation, as will be apparent hereinafter.

The external surface means 71 of the exchangeable collar means 30 forms the extruding surface means of the mandrel means 29 and defines a first forward cylindrical portion 72 adapted to define the internal surface of the extruded tubular member 11 and a second rear cylindrical portion 73 spaced from the first cylindrical portion 72 by an inwardly directed stepped part 74 for a purpose hereinafter described, the stepped part 74 in the embodiment of FIGURES 1-8 defines a substantially frustoconical intermediate portion 74 as illustrated.

When the collar means 30 have been telescoped onto the free end 58 of the piercing and extruding mandrel means 31 in the manner illustrated in FIGURE 6, the rear end surface 66 thereof is adapted to abut against the shoulder means 59 of the adapter 31 whereby a nut means 75 of this invention is adapted to be threaded on the threaded portion 61 of the free end 58 of the mandrel means 29 and have its rear flat end surface 76 engage against the front end surface 65 of the collar means 30 to compact the collar means 30 in stacked relation against the shoulder means 59 of the adapter 31 so that the collar means 30 will be properly positioned on the mandrel means 29 and be held in that position by the nut means 75 during the piercing and extruding operation hereinafter described. However, it can readily be seen that should the collar means 30 become damaged, worn or otherwise changed to adversely affect subsequent extruding operations, the collar means 30 can be readily removed from the mandrel means 29 by merely loosening and removing the nut means 75 so that another collar means 30 can be replaced on the mandrel means 29 in the manner previously described without requiring a time-consuming and expensive mandrel means dismantling operation as in prior known extruding apparatus.

If desired, the nut means 75 of this invention can include an internally threaded bore 77 passing longitudinally therethrough with the forward part 78 being suitably shaped to provide tool grasping means for threading the same onto and off the threaded portion 61 of the free end 58 of the mandrel means 29. The rear part 79 of the nut means 75 can be substantially cylindrical with a diameter smaller than the diameter of the cylindrical part 72 of the collar means 30 so that the resulting extruding tubular length 11 can pass over the nut means 75 without interference therefrom.

In addition, the forward part 78 of the nut means 75 can have a beveled leading surface means 80 to facilitate the billet piercing operation in a manner hereinafter described and complement the piercing end 64 of the mandrel means 29 in the manner illustrated in FIGURE 6. Also, the rear surface means 76 of the nut means 75 can be provided with an annular stress relieving recess 81 adjacent the threaded bore 77 thereof so that when the nut means 75 tightly compacts the collar means 30 against the shoulder means 59 of the adapter 31, the compression forces resulting therebetween 0n the adapter 31 will be relieved by the previously described beveled surfaces and annular grooves, as illustrated.

From the above, it can be seen that the apparatus of this invention has a relatively few operating parts while still permitting the same to extrude tubular members, such as pipes or the like, from a solid metallic billet 12, the tubular members 11 being in the order of forty feet in length or the like.

The operation of the method and apparatus 10 of this invention will now be described.

As illustrated in FIGURE 1, the stem 37 and piercing and extruding mandrel means 29 are moved away to the right from the housing 13 of the apparatus 10 so that a heated billet 12 can be placed in the cavity of the housing 13 with the end 28 disposed against the external die means 27 of the apparatus 10.

Thereafter, the extruding and piercing mandrel means 29 and hollow stem 37 are moved to the position illustrated in FIGURE 1 to close ofi" the right-hand end of the cavity 15 of the housing 13, with the dummy block disposed between the stem 37 and the end 48 of the billet 12.

Thereafter, with the hollow stem 37 initially held stationary in the position illustrated in FIGURE 1, the piercing and extruding mandrel means 29 is moved to the left from the position illustrated in FIGURE 1 whereby the free end 58 and collar means 30 thereof pierce the solid billet 12 in the manner illustrated in FIGURE 2 to form a bore 82 substantially therethrough. However, as the free end 58 pierces through the billet 12, the same forces a slug 83 of material through the external die means 27 in the manner illustrated in FIGURE 2 until the collar means 30 has the extruding surface means 71 thereof disposed in the desired position relative to the external die means 27 in the manner illustrated in FIG- URE 6.

When the free end 58 and collar means 30 pierce through the billet 12 to the position illustrated in FIG- URE 6, further movement of the piercing and extruding mandrel means 29 is terminated and the collar means 30 is held in the position illustrated in FIGURE 6 during the resulting extruding operation whereby it can be seen that the slug 83 extruded from the billet 12 is integrally interconnected to the billet 12 by an annular portion of material 84 in the manner illustrated in FIGURE 2.

After the collar means 30 has reached the position illustrated in FIGURE 2, the hollow stem 37 is moved to the left from the position illustrated in FIGURE 2 to the position illustrated in FIGURE 5, whereby it can be seen that the stem 37 pushes the dummy block 47 to the left to cause the billet 12 to extrude through the annular cavity defined between the external die means 27 and the extruding surface means 71 of the collar means to provide the tubular member 11.

However, as the tubular member 11 is being extruded from the billet 12 in the manner illustrated in FIGURE 5, it can be seen that the tubular member 11 has the leading end thereof closed by the slug 83 whereby a vacuum condition is created in the tubular member 11 as the same is being extruded to the left in the manner previously described.

If this vacuum condition in the tubular member 11 were permitted to continue to exist, the same will subsequently cause a complete inward collapse of at least part of the extruded portion of the tubular member 11 because of the external air pressure surrounding the same whereby a substantial quantity of tubular stock 11 would have to be scrapped.

However, according to the teachings of the invention set forth and claimed in the copending patent application, Ser. No. 317,521, filed Oct. 21, 1963 and assigned to the same assignee to whom this application is assigned, a projectile shooting means 86 is carried by the collar means 18 of the apparatus 10 and is adapted to shoot a projectile completely through the tubular member 11 at a point disposed intermediate the slug 83 and the free end 58 of the piercing and extruding mandrel means 29 in the manner illustrated in FIGURE 5 to define vent passages 87 in the tubular member 11 to relieve the vacuum condition existing therein whereby the vacuum condition in the extruded tubular member 11 can be completely eliminated before the-tubular member 11 emerges from the apparatus 10.

In this manner, it can be seen that the initial vacuum condition existing in the tubular member 11 will not adversely affect the resulting tubular member 11 even though the same is extruded to a considerable length, such as forty feet or the like.

After the tubular member 11 has been extruded from the billet 12 in the manner previously described, the tubular member 11 is removed from the apparatus 10 and the slug end 83 thereof is severed from the tubular member 11 whereby the tubular member 11 can be shipped, stored or further machined as desired.

The cut slug 83 can then be utilized as a solid billet in another apparatus 10 which extrudes a smaller diameter tubular member 11 than the apparatus 10 illustrated in the drawings whereby no Waste of metallic material is provided by the method and apparatus 10 of this invention.

Further, should a particular portion of the cylindrical part 72 of the collar means 30 of the piercing and extruding mandrel means 29 become worn after many billets 12 have been pierced and extruded by the same in the above manner, it can be seen that by merely making a simple adjustment on the ram means operating the piercing and extruding mandrel means 29, the collar means 30 thereof can come to rest relative to the external die means 27 in a new position thereof whereby a new portion of the surface of the cylindrical part 72 thereof will cooperate with the die means 27 to extrude the tubular member 11 in the manner previously described.

In addition, should the entire surface of the cylindrical part 72 of the coller means 30 subsequently become worn so that the tubular member 11 extruded thereby will not have the desired wall thickness, the collar means 30 can be readily and simply removed from the mandrel means 29 in the manner previously described and be machined down to provide a collar means 30 for another apparatus 10 which extrudes a smaller diameter tubular member 11 whereby it can be seen that the life of one collar means 30 for the apparatus 10 of this invention can be relatively long.

While the apparatus 10 illustrated in the drawings and previously described is being utilized for extruding a cylindrical tubular member 11, because of the configuration of the collar means 30 in the manner illustrated in FIGURE 7, it is to be understood that the collar means 30 could be so constructed and arranged in cooperation with a modified external die means 27 that the apparatus 10 of this invention could extrude a tubular member 11 having any desired cross-sectional configuration, such as rectangular or the like.

While it has been previously stated that most prior known extruding apparatus cannot be utilized to extrude tubular members from solid metallic billets formed of the softer aluminum alloys because of the aforementioned build-up of material on the prior known piercing and extruding mandrel means, it has been found that the substantially bullet-shaped end portion 64 of the mandrel means 29 of this invention in combination with the exchangeable extruding surface means 30 of this invention substantially eliminates the build-up problem whereby the apparatus 10 of this invention is readily adapted to extrude tubular members from solid billets of soft aluminum alloys, such as aluminum alloys 6063, 6061, 3003, as well as the soft aluminum alloys in the 1000 series.

In particular, the soft aluminum alloys tend to load up on conventional piercing mandrel means because of the difference in the hardness of the alloys at extrusion temperatures making the alloys substantially sticky or gummy so that layers thereof build up on the piercing part of the mandrel means to such an extent that the same affects not only the inside dimensions of the resulting tubular members, but also the internal surface configurations thereof whereby further extrusion operations must be terminated until the built-up layers are mechanically or chemically cleaned therefrom in a costly and time consuming manner.

However, it has been found that such build up of the softer aluminum alloys on the free end means 58 of the mandrel means 29 of this invention are substantially eliminated so that the apparatus 10 of this invention can readily extrude tubular members from solid billets formed from the softer aluminum alloys.

Of course, the apparatus of this invention can also extrude tubular members in the above manner from solid billets of harder aluminum alloys as well as from solid billets formed of other metallic and desired materials.

As previously stated, one of the problems encountered in piercing and extruding solid metallic billets is the fact that relatively large inwardly directed radial forces are imposed on the piercing and extruding mandrel means by the billet which tend to force the mandrel means in the direction of the subsequent extruding operation because the billet can only extrude in such direction whereby adverse forces are placed on the threaded connections between the adaptors of the mandrel means, such as between the adaptors 31, 32, 33, 34 and 35 of the mandrel means 29 previously described.

However, it has been found according to the teachings of this invention that by providing the inwardly directed stepped part 74 on the collar means 30 adjacent the extruding cylindrical surface means 72 thereof, the forces created during the piercing and extruding operation act against such stepped part 74 to substantially offset the forces of the billet 12 that tend to force the mandrel means 29 to the left in the drawings whereby the aforementioned adverse forces on the coupling connections between the adaptors of the mandrel means is substantially reduced or eliminated whereby the life of the mandrel means 29 of this invention is substantially increased.

While the stepped part 74 of the collar means 30 previously described has been illustrated as being a substantially frusto-conical stepped portion to more readily facilitate the aforementioned piercing operation, it is to be understood that the stepped part 74 could have other configurations and still relieve the aforementioned adverse forces that tend to separate the adaptors of the mandrel means 29 during the piercing and extruding operations.

For example, reference is made to FIGURES 9 and 10 wherein another embodiment of the mandrel means and extruding collar means of this invention are provided and parts thereof similar to like parts of the mandrel means 29 and collar means 30 previously described are indicated by like reference numerals followed by the reference letter A.

As illustrated in FIGURES 9 and 10, the mandrel means 29A is identical to the mandrel means 29 previously described except that the collar means 30A carried thereby has a different inwardly directed ste ped part 88 disposed between and interconnecting together the cylindrical surface means 72A and 73A thereof.

The stepped part 88 of the collar means 30A defines a small radius 89 adjacent the larger cylindrical surface means 73A and has a substantially radially inwardly disposed surface 90 joining the smaller cylindrical surface means 72A at substantially a right angle relative thereto.

In this manner, it can be seen that the forces created between the die means 26A, 27A and the collar means 30A of the mandrel means 29A will act against the stepped part 88 thereof to relieve or oppose the forces of the billet 12A that tend to separate the various parts of the mandrel means 29A in a leftward direction during both the piercing and extruding operation.

While the stepped part 88 of the collar means 30A is illustrated as being relatively small in height, it is to be understood that the stepped part 88 could be taller as desired as well as have another configuration as desired.

Therefore, it can be seen that not only does this invention provide an improved apparatus for extruding a hollow tubular member from a solid metallic billet or the like, but also this invention provides improved parts for such an apparatus or the like.

While the form of the invention now preferred has been disclosed as required by the statutes, other forms may be used, all coming within the scope of the claims which follow:

What is claimed is:

1. In an apparatus for piercing and extruding a solid metallic billet through a female die means to form an extruded tubular length, the improvement comprising a mandrel means having a tip means for piercing into said solid billet until said tip means is telescoped into said female die means to a predetermined position relative thereto to define an annular cavity between an extruding surface means of said tip means and said female die whereby said billet can be extruded through said annular cavity to form said extruded tubular length, said mandrel means having a free end forming part of said tip means thereof, said mandrel means having an exchangeable collar means telescoped onto said free end of said mandrel means to be carried thereby, said collar means having an exterior surface defining said extruding surface means of said tip means, said mandrel means having means holding said collar means from movement relative thereto during said piercing and extruding operations.

2. In an apparatus as set forth in claim 1, said mandrel means having a shoulder means spaced inwardly from said free end thereof and defining part of said holding means of said mandrel means, said collar means having a shoulder means abutting said shoulder means of said mandrel means to properly position said extruding surface means relative thereto.

3. In an apparatus as set forth in claim 2, said free end of said mandrel means having an externally threaded portion, and a nut means threaded on said threaded portion to hold said shoulder means of said collar means in abutting relation with said shoulder means of said mandrel means whereby said nut means defines part of said holding means of said mandrel means.

,4. In an apparatus as set forth in claim 3, said free end of said mandrel means including a substantially bullet-shaped forward part disposed outboard of said threaded portion thereof to form the leading piercing part of said mandrel means.

5. In an apparatus as set forth in claim 3, said collar means having a substantially cylindrical bore passing therethrough, said free end of said mandrel means having a substantially cylindrical part outboard of said shoulder means thereof and being telescopically disposed in said bore of said collar means to hold said collar means in the proper axial position relative to said mandrel means whereby said cylindrical part defines part of said holding means of said mandrel means.

6. In an apparatus as set forth in claim 5, said free end of said mandrel means having stress relieving annular recesses provided in the exterior thereof on each side of said cylindrical part thereof and respectively adjacent said shoulder means and threaded portion thereof.

7. In an apparatus as set forth in claim 6, said collar means having opposed ends interrupted by said bore thereof, said opposed ends respectively having beveled surfaces at said bore.

8. In an apyaratus as set forth in claim 3, said nut means having a beveled front surface to facilitate said piercing action of said mandrel means into said solid billet.

9. In an apparatus for piercing and extruding a solid metallic billet through a female die means to form an extruded tubular length, the improvement comprising a mandrel means having a tip means for piercing into said solid billet until said tip means is telescoped into said female die means to a predetermined position relative thereto to define an "annular cavity between an extruding surface means of said tip means and said female die whereby said billet can be extruded through said annular cavity to form said extruded tubular length, said mandrel means having a free end forming part of said tip means thereof, said mandrel means having an exchangeable collar means telescoped onto said free end of said mandrel means to be carried thereby, said collar means having an exterior surface defining said extruding surface means of said tip means, said mandrel means having a shoulder means spaced inwardly from said free end thereof, said collar means having a shoulder means abutting said shoulder means of said mandrel means to properly position said extruding surface means relative thereto, said shoulder means of said collar means being larger in diameter than the diameter of said shoulder means of said mandrel means.

10. In an apparatus for piercing and extruding a solid metallic billet through a female die means to form an extruded tubular length, the improvement comprising a mandrel means having a tip means for piercing into said solid billet until said tip means is telescoped into said female die means to a predetermined position relative thereto to define an annular cavity between an extruding surface means of said tip means and said female die whereby said billet can be extruded through said annular cavity to form said extruded tubular length, said mandrel means having a free end forming part of said tip means thereof, said mandrel means having an exchangeable collar means telescoped onto said free end of said mandrel means to be carried thereby, said collar means having an exterior surface defining said extruding surface means of said tip means, said mandrel means having a shoulder means spaced inwardly from said free end thereof, said collar means having a shoulder means abutting said shoulder means of said mandrel means to properly position said extruding surface means relative thereto, said free end of said mandrel means having an externally threaded portion, and a nut means threaded on said threaded portion to hold said shoulder means of said collar means in abutting relation with said shoulder means of said mandrel means, said mandrel means having a first substantially cylindrical part defining said shoulder means thereof and having a second substantially cylindrical part larger than said first part and spaced therefrom by an inwardly directed stepped part of said mandrel means.

11. In an apparatus for piercing and extruding a solid metallic billet through a female die means to form an extruded tubular length, the improvement comprising a mandrel means having a tip means for piercing into said solid billet until said tip means is telescoped into said female die means to a predetermined position relative thereto to define an annular cavity between an extruding surface means of said tip means and said female die whereby said billet can be extruded through said annular cavity to form said extruded tubular length, said mandrel means having a free end forming part of said tip means thereof, said mandrel means having an exchangeable collar means telescoped onto said free end of said mandrel means to be carried thereby, said collar means having an exterior surface defining said extruding surface means of said tip means, said exterior surface of said collar means defining a first substantially cylindrical part thereof and a second substantially cylindrical part thereof spaced from said first part by an inwardly directed stepped part of said collar means.

12. In an apparatus as set forth in claim 11, said first cylindrical part of said collar means being the forward part of said extruding surface means and being smaller in diameter than the diameter of said second cylindrical part.

13. In an apparatus as set forth in claim 12, said collar means having flat parallel end surfaces respectively disposed adjacent said cylindrical parts of said exterior surface and disposed perpendicular relative thereto.

14. In an apparatus as set forth in claim 13, said collar means having a substantially cylindrical bore passing longitudinally therethrough and interrupting said fiat end surfaces thereof whereby said free end of said mandrel means is telescopically disposed in said bore and extends from each end surface of said collar means.

15. In an apparatus as set forth in claim 14, said end surfaces of said collar means respectively having beveled parts adjacent said bore thereof, the leading end surface of said collar means having its outer edge also beveled.

References Cited UNITED STATES PATENTS 1,330,489 2/1920 Neuberth 72-273 2,339,019 1/ 1944 Le Tourneau 72-266 2,358,838 9/1944 Wadell 72-481 2,359,339 10/1944 Wadell 72-481 2,903,130 9/1959 Reichl 72-264 RONALD D. GREFE, Priamry Examiner US. Cl. X.R. 72-273 

